This invention relates to a device for producing lines or groups of lines of electromagnetic radiation of the optical spectral range in a definable area of space. The lines or groups of lines can be used as positioning aids or geometry detection aids, and they include at least one conversion unit which is at least partially transparent to the electromagnetic radiation used, and which can convert the electromagnetic radiation passing through it, especially coherent radiation or laser radiation, such that the electromagnetic radiation forms at least one line or group of lines in a given three-dimensional area.
A device of this type is used, for example, to give to a robot a positioning aid for machining of a workpiece, or to make available to the robot a recognition aid for the contour or the geometry of a workpiece. Generally, the electromagnetic radiation is laser light which passes through the conversion unit into the stipulated three-dimensional area located, for example, on the workpiece such that on the workpiece for the robot, recognizable groups of lines are copied in the form of a planar orthogonal grid. Using these groups of lines, made for example as grids, the robot is enabled to machine the workpiece at given points.
Conversion units in the past are diffractive elements such as holograms which can diffract parts of the laser light penetrating the conversion unit, such that in the given three-dimensional area, for example, on the workpiece, lines, or for example, grid-shaped groups of lines form. One defect, in the past embodiments of the conversion unit using diffractive elements, is that a substantial portion of the electromagnetic radiation is diffracted into undesirable orders so that generally far less than 50% of the electromagnetic radiation incident on the conversion unit contributes to producing lines or groups of lines. Furthermore, when the conversion unit is equipped with diffractive elements, it is disadvantageous that only very small widening angles can be achieved, so that only in a relatively small range of solid angles behind the conversion unit, can lines or groups of lines be produced.
The object of this invention is to devise a device of the initially mentioned type which is made to be more efficient.
This is achieved as depicted in the invention, in that the conversion unit includes at least one refractive element. By refraction of the radiation passing through the conversion unit, on at least one optically functional interface of the refractive element, at least one line or group of lines is formed in the given three-dimensional area. When using a refractive element, much higher efficiencies of almost 100% can be achieved. Furthermore, refractive elements make it possible to dramatically broaden the electromagnetic radiation incident on the conversion unit, so that the desired lines, or groups of lines, can be formed in an essentially larger range of solid angles behind the conversion unit.
To do this, the optically functional interface of at least one refractive element can have a freely selectable configuration which is suitable for the lines, or line groups, to be produced. It is, for example, possible to divide the optically functional interface of at least one refractive element into segments. In this case, the segments can have the same size and can be shaped to be identical.
According to one preferred embodiment of this invention, the individual segments can have a cylinder lens geometry, there being, preferably, two groups of segments with cylinder axes of cylindrical geometry perpendicular to one another. The cylinder lens geometry of the individual segments can be a spherical, or an aspherical, cylinder lens geometry. Especially in the choice of these cylinder lens geometries, is it possible to widen the electromagnetic radiation passing through the conversion unit behind the latter into a solid angle of up to, or even more than, 180xc2x0. For example, groups of crossed lines can be formed, by the arrangement of individual segments of the optically functional interface, as cylinder lens segments with cylinder axes perpendicular to one another and can form a grid-like structure, as for example, a planar orthogonal grid with a correspondingly array-like arrangement of the refractive elements.
It is possible, as depicted in the invention, for the produced lines to be straight or even curved lines. Furthermore, it is possible for the generated groups of lines to be crosses, triangles, polygons or grids, and the lines which form the individual groups of lines can be at a right, or at a non-right angle to one another.
According to one preferred embodiment of this invention, the generated lines or groups of lines are curved such that upon incidence on a curved surface of a workpiece in a given three-dimensional area on this workpiece, they form a planar structure, especially a planar, orthogonal grating. It is, for example, conceivable that in machining robot machines, the workpiece removes material from the workpiece with the aid of the aforementioned inherently curved grid structure until the sensors of the robot detect that the line structure which is incident on the machined curved surface of the workpiece forms a planar orthogonal grid. The conversion unit, encompassed by the device as depicted in the invention, causes distortion of the traversing electromagnetic radiation which is distorted by a correspondingly curved workpiece such that a clearly detectable structure like a planar orthogonal grid is formed.
It is possible for the device to include a source for producing electromagnetic radiation, especially a laser light source. The device together with the laser light source can be used either as a separate unit or can, for example, be installed in a corresponding robot for machining of workpieces.
It is also possible to use one such device for process monitoring, for example, to monitor a welding process, here especially, an application in conjunction with CMOS cameras is suitable, because these CMOS cameras have much higher dynamics so that among others both the welding point and also its vicinity can be better recognized, so that, for example, the lines, or groups of lines, imaged on the workpiece to be welded can be better recognized by the welding unit, or the process monitoring unit. Other possible applications of a device as depicted in the invention are in the area of surface analysis or three-dimensional assignment, especially tracking of a system.